Resilient bobbin



United States Patent RESILIENT BOBBIN Eric Brown Davidson, London,England, assignor to Davidson Springs Limited, London, England, a Bntishcompany Application September 20, 1955, Serial No. 535,437

Claims priority, application Great Britain September 21, 1954 2 Claims.(Cl. 242-11811) This invention relates to skeleton cores or bobbins ofthe kind composed of a helical spring encased within a cage-like sheathformed by a length of wire laced progressively around adjoining coils ofthe spring from one end of the latter.

Such skeleton core or bobbin structures are commonly employed in thetreatment of textile fibres which are wound thereon into the form of acheese or cop. For this purpose the skeleton structure is mounted on amandrel which must be a tight fit within the structure to preventslippage. To obtain an efiective frictional grip it is, however,necessary for the known skeleton structures to be made exactly to fitthe mandrel, within very narrow limits, and this gives rise to seriousmanufacturing ditficulties.

A main object of the invention is largely to obviate the need for exactfitting, thereby avoiding the aforementioned difliculties. Accordinglythe invention provides a skeleton core structure composed of a helicalspring encased within a cage-like sheath formed by a length of wirelaced progressively, in substantially equally spaced turns, aroundadjoining coils of the spring from one end of the latter to permitlimited radial spring movement, the characteristic feature being thatthe said lacing is applied whilst the spring is radially expanded underan externally applied torsional force and acts, by abutment betweenoppositely directed lacing turns around individual spring coils, whensaid force is removed, to prevent the laced spring returning to theposition which would, but for the lacings, be its neutral position ofrest, whereby the whole of said permitted spring movement is availablefor further radial expansion of the spring.

In order that the invention may be clearly understood and readilycarried into eflect an embodiment thereof will now be described indetail with reference to the accompanying drawings in which:

Figure 1 is a side elevational view showing a skeleton core or bobbinstructure laced in accordance with the invention, part of the lacingbeing broken away for purposes of clarity, and

Figure 2 is a view similar to Figure l but showing the structure inposition over a mandrel, the latter being in chain-dotted lines.

Referring now to the drawings, a skeleton core or bobbin structure iscomposed of a main helical spring 1 and a lacing wire 2 which is boundin uniform zig-zag turns 2a around adjoining coils of the spring 1 overthe whole length of the spring so that the spring coils ice pass throughturn loops 2b in the lacing wire which are directed alternately towardsopposite ends of the spring. Each end 20 of the lacing wire is firmlysecured to the adjoining end of the spring and the lacing turns 2a arespaced along adjoining spring coils to permit twisting of the spring andconsequential radial movement of the laced structure over a limitedrange determined by the spacing of the lacing turns. Inthe drawings onlyone end 20 of the lacing wire 2 is shown but it will be appreciated thatthe opposite wire end is secured in exactly the same manner to theopposite end of the helical spring 1.

The lacing wire 2 is applied to the spring 1 whilst the latter istwisted in the direction of unwinding and thus radially expanded undertorsion. The reaction of the spring, therefore, when the expansive forceis removed, tends radially to contract the structure to the neutralposition of rest of the spring but this is prevented by abutment beweenadjoining oppositely directed lacing loops 2b around each spring coil asillustrated in Figure 1. The structure is conveniently dimensioned sothat, when thus held under torsion by the lacing, the minimum internaldiameter is slightly less than the external diameter of a mandrel 3 tobe fitted therein so that the structure has to be further radiallyexpanded to receive the oversize mandrel. Such radial expansion iseffected by turning the lower end of the spring 1 in the direction ofthe arrow A and, at the same time, either holding the upper spring endor turning this upper end in the opposite direction. As a result, thespring will be ultimately under considerable torsion as shown in Figure2 and will exert a very firm grip on the inserted mandrel 3.

With the foregoing arrangement, the mount by which the external diameterof the mandrel 3 exceeds the internal diameter of the laced structurecan vary sufli-' ciently to provide adequate manufacturing tolerancessince virtually the whole range of permitted radial movement of thestructure will be available in the expansive direction to permit entryof the mandrel.

I claim:

1. A skeleton core structure comprising a radially expanded helicalspring, and a length of wire laced progressively in substantiallyequally spaced turns around adjoining coils of the spring from one endof the latter to the other, said turns being spaced to maintain thespring in a partially expanded condition by abutment of adjacent turns,the spacing of adjacent turns permitting a determinable radial expansionof the spring.

2. A skeleton core structure as claimed in claim 1 in combination with amandrel having an external diameter which is slightly oversize inrelation to the minimum internal diameter of the laced structure,whereby the latter has to be further radially expanded againstconsiderable spring reaction to fit over the mandrel which is thengripped firmly by the structure.

References Cited in the file of this patent UNITED STATES PATENTS

